Ok, was the original engine a 3.8?
If not you may need to have the computer flashed.
The Cam, Crank Sensor and the PCM could be getting mixed signals if PCM is programed for different engine.
If the Builder does rebuilds on a regular basis I would almost agree the chance of the Cam or Crank being misaligned is slim. However, it can still happen.
Since it is a DIS System it could also be possible that either or even both the Cam and Crank Sensors are out of Spec and just not totally bad since no codes for them.
Here is more on the DIS System.
DIS COIL CHECKS
The coils in DIS ignition systems function the same as those in ordinary ignition systems, so testing is essentially the same. But the driveability symptoms caused by a weak coil or dead coil will be limited to one or two cylinders rather than all the cylinders. Many DIS systems use the "waste spark" setup where one coil fires a pair of spark plugs that are opposite one another in the firing order. Others, including the newer coil-over-plug systems, have a separate coil for each spark plug.
Individual DIS coils are tested in essentially the same way as epoxy-filled (square-type) ignition coils. First, isolate the coil pack by disconnecting all the leads. Set the ohmmeter in the low range, and recalibrate if necessary. Connect the ohmmeter leads across the ignition coil primary terminals, and compare the primary resistance reading to specifications (typically less than 2 ohms). Then connect the ohmmeter leads across the coil secondary terminals and compare the secondary resistance reading to specifications (typically 6,000-30,000 ohms). If readings are outside the specified range, the coil is defective and needs to be replaced.
If measuring the secondary resistance of a DIS coil is difficult because of the coils location, try removing the wires from the spark plugs and measure secondary resistance through the plug wires rather than at the secondary terminals on the coils. Just remember to add in a maximum of 8,000 ohms of resistance per foot for the plug wires.
DIS MODULE & SENSOR CHECKS
Here is a little trick that will literally show you if a DIS module and its crankshaft sensor circuit are working: connect a halogen headlamp to the spade terminals that mate the DIS module to the coils. A headlamp is recommended here because it puts more of a load on the module than a test lamp. If the headlamp flashes when the engine is cranked, the DIS module and crankshaft position sensor circuit are functioning. Therefore, the problem is in the coils.
If the headlamp does not flash, or there is no voltage to the module or coil pack when the engine is cranked, the problem is most likely in the crankshaft sensor circuit. On most vehicles, a bad crank position sensor will usually set a fault code, so use a scan tool to check for a code. Or, check the crank sensor itself.
Magnetic crank sensors can be tested by unplugging the electrical connector and checking resistance between the appropriate terminals. If resistance is not within specs, the sensor is bad and needs to be replaced.
Magnetic crank position sensors produce an alternating current when the engine is cranked so a voltage output check is another test that can be performed. With the sensor connected, read the output voltage across the appropriate module terminals while cranking the engine. If you see at least 20 mV on the AC scale, the sensor is good, meaning the fault is probably in the module. If the output voltage is low, remove the sensor and inspect the end of it for rust or debris (magnetic sensors will attract iron and steel particles). Clean the sensor, reinstall it and test again. Make sure it has the proper air gap (if adjustable) because the spacing between the end of the sensor and the reluctor wheel or notches in the crankshaft will affect sensor output voltage. If the air gap is correct and output is still low, replace the sensor.
Hall effect crankshaft position sensors typically have three terminals; one for current feed, one for ground and one for the output signal. The sensor must have voltage and ground to produce a signal, so check these terminals first with an analog voltmeter. Sensor output can be checked by unplugging the DIS module and cranking the engine to see if the sensor produces a voltage signal. The voltmeter needle should jump each time a shutter blade passes through the Hall effect switch. If observed on an oscilloscope, you should see a square waveform. No signal would tell you the sensor has failed.
DIS PERFORMANCE PROBLEMS
In instances where the engine starts and runs but does not perform well (lack of power, poor fuel economy, spark knock, elevated emissions, etc.), The problem may be outside the DIS system. First, the individual coils should be tested to make sure their primary and secondary resistance is within specs. If the coils are all okay, the electronic spark control circuit may be receiving bad information from another sensor.
Low MAP sensor output voltage or a coolant sensor that reads cold all the time will allow more spark advance than normal. This, in turn, may cause detonation (spark knock) problems when the engine is under load. So too can a faulty knock sensor or an EGR valve that is not working.
High MAP output voltage or a misadjusted throttle position sensor can have the opposite effect and cause the spark control system to retard timing more than normal. Retarded timing will reduce performance and fuel economy.
Do not forget, too, that ordinary secondary ignition problems can also cause misfires with DIS the same as a conventional ignition system. A bad spark plug wire or a worn or fouled spark plug will act just like a weak or bad DIS coil. So anytime you find an ignition problem that is isolated to a single cylinder, remove and inspect the spark plug and plug wire to rule out those possibilities.
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Saturday, May 22nd, 2010 AT 3:15 PM
